Lithium-rich Layered Oxide Cathode Research Articles

Effect of Rare Earth Ion Doping on the Performance of Lithium-Rich Cathode Materials for Lithium-Ion Batteries

Lithium-rich layered oxide cathode materials have the advantages of a high voltage and a high specific capacity. Their commercial applications have however been impeded by some disadvantages such as low initial coulombic efficiency and low cycle life. To overcome these issues, rare earth ion-doped lithium-rich layered oxide cathode materials are investigated in this work. The irreversible release of O2- in Li2MnO3 is suppressed by rare earth ions doping, which enhanced the initial coulombic efficiency of the materials. Meanwhile, the rare-earth ion radius used for doping is larger than the Mn4+ radius, which enlarges the (003)-crystalline plane spacing, resulting in a significant enhancement of the rate performance of the material.

Performance improvement strategies of boron-doped lithium-rich layered oxide cathode materials for wide temperature condition

Herein, the boron-doped Li-rich materials are prepared by rapid nucleation-assisted solvothermal and high-temperature method. In this work, the effects of boron doping on crystal structure and cycling performances of as-prepared materials were investigated. The material characterization results show that the introduction of B reduces the TM valence, enlarges the (003) space distance, and modulates the local crystal structure, which may change the electrochemical performance of as-prepared samples. Li1.2Ni0.24Co0.08Mn0.48B0.02O2 (LLNCMBO-2) showed an increase in discharge capacity of 36.5 mAh g−1 at 0.1 C compared to the pristine sample. The LLNCMBO-2 exhibit high capacity retention of 85.50 % after 200 cycles with a voltage decay of only 254.9 mV. Additionally, the results of wide temperature testing show that the electrochemical performance of boron-doped samples improved evidently.

Lithium-rich manganese-based layered oxide cathode materials for lithium-ion batteries modified by MoS2 coatings with two-dimensional graphene-like structures

Lithium-rich manganese-based layered oxide cathode materials (LRMCs) have some unique advantages such as high theoretical capacity (≥ 250 mAh g-1) and high energy density. Therefore, they are deemed as a kind of cathode material for lithium-ion batteries with an excellent prospect of application. However, the redox of oxygen anion is able to generate irreversible lattice oxygen loss, leading to the irreversible loss of capacity, bringing about a sharp drop in working voltage, and seriously restricting the commercialization of LRMCs. In this paper, MoS2 coating with two-dimensional graphene-like structure is coated on the surface of LRMCs material for improving the cycling stability and rate performance of the material. The MoS2 coating can provide a two-dimensional diffusion channel for the migration of lithium-ions, which facilitates the fast release of lithium-ions during cycling process. The results show that the first discharge capacity, initial Coulomb efficiency and rate performance of LRMCs were improved. When the current density is 1C, the first discharge specific capacity of LRMCs@MoS2 reaches 227.69 mAh g-1, and the capacity retention ratio is 84.98% after 100 cycles. When the current density is 5C, it can still provide a discharge specific capacity of 137.87 mAh g-1, demonstrating excellent electrochemical performance. This study comes up a simple and practical idea to realize the modification of cathode materials for high performance lithium-ion batteries.

Comprehensive Review of Li-Rich Mn-Based Layered Oxide Cathode Materials for Lithium-Ion Batteries: Theories, Challenges, Strategies and Perspectives.

Lithium-rich manganese-based layered oxide cathode materials (LLOs) have always been considered as the most promising cathode materials for achieving high energy density lithium-ion batteries (LIBs). However, in practical applications, LLOs often face some key problems, such as low initial coulombic efficiency, capacity/voltage decay, poor rate performance and poor cycle stability. It seriously shortens the lifespan of lithium-ion batteries and hinder the large-scale commercial application of LLOs. Herein, firstly, the basic theories of LLOs were systematically reviewed, including the structural characteristics, the working mechanism of LLOs, the preparation methods of LLOs (liquid phase co-precipitate method, sol-gel method, hydrothermal synthesis method, solid phase method, low heat solid-phase method, high temperature solid-state method etc.), and electrochemical characteristics of LLOs (first charge discharge characteristics and reversible efficiency, cycling performance, high and low temperature performance and thermal stability etc.). Then, key challenges faced by LLOs were systematically discussed. Finally, the LLOs modification strategies used to address these challenges (element doping, surface modification, defect engineering, structural and morphological control etc.) were elaborated in detail. This important review provides potential insights and directions for further improving the electrochemical performance of LLOs, and provides a necessary theoretical basis for accelerating the large-scale commercial application of LLOs. It possesses important scientific research value and far-reaching social significance.

A novel low-cobalt single-crystal lithium-rich manganese-based layered oxide cathodes with enhanced electrochemical performances

Single-crystal (SC) morphology of lithium-rich manganese-based layered oxides (LLOs) cathode materials, due to their stable structure and absence of excess grain boundaries, holds promise for addressing issues such as oxygen loss and poor cycle stability in traditional polycrystalline (PC) cathode materials. In this study, a low-cobalt SC LLOs cathode material with excellent electrochemical performances is successfully synthesized by the molten salt method and the appropriate calcination temperature. The SC LLOs cathode calcined at 900 °C exhibits superior physical properties. Its particle size of D50 is 332 nm, which results in an optimal average Li+ diffusion coefficient (DLi+) value of 10−10.29 cm2 s−1. At C/10 (1C = 250 mA g−1), it delivers the first discharge capacity of 242 mAh g−1 with an initial Coulombic efficiency (ICE) of 73.8 %. After 200 cycles at C/3, it maintains the capacity retention of 80.8 %. This work extensively elaborates on the influence of calcination temperature on the particle size, physical properties and electrochemical stability of low-cobalt SC LLOs cathode materials, which would provide effective guidance for the design of high-performance SC cathode materials.

Rapid lithium-ion insertion/extraction and migration behavior of Na2WO4-encapsulated lithium-rich layered oxide cathode

Rapid lithium-ion insertion/extraction and migration behavior of Na2WO4-encapsulated lithium-rich layered oxide cathode

Stable surface lattice for prolonged cycle life of single-crystal lithium-rich layered oxide cathodes

Lithium-rich layered oxides (LLOs) have garnered significant attention due to their outstanding capacity. However, the severe capacity fading resulting from lattice deterioration initiated at the surface constrains the further advancement of LLOs. Here, we present a method to stabilize the surface lattice to enhance the capacity stability of LLOs. Specifically, we have engineered a nanometer-thin Gd-doped NiO rock-salt epitaxial layer on the surface of single-crystal LLOs, along with an atomic-level thickness LiGdO2coating layer. The dual-nanolayer protection strategy has successfully stabilized the surface structure of LLOs and suppressed electrode–electrolyte interface side reactions. As a result, the modified sample achieves a capacity retention rate of 93.4% after 500 cycles at 1C and 94.2% after 200 cycles at 0.2C. Our study underscores the importance of surface structure in achieving high cyclic stability in LLOs and provides an important approach for designing stable lithium-ion battery cathode materials.

Advanced TiO2/Al2O3 Bilayer ALD Coatings for Improved Lithium-Rich Layered Oxide Electrodes.

Surface modification is a highly effective strategy for addressing issues in lithium-rich layered oxide (LLO) cathodes, including phase transformation, particle cracking, oxygen gas release, and transition-metal ion dissolution. Existing single-/double-layer coating strategies face drawbacks such as poor component contact and complexity. Herein, we present the results of a low-temperature atomic layer deposition (ALD) process for creating a TiO2/Al2O3 bilayer on composite cathodes made of AS200 (Li1.08Ni0.34Co0.08Mn0.5O2). Electrochemical analysis demonstrates that TiO2/Al2O3-coated LLO electrodes exhibit improved discharge capacities and enhanced capacity retention compared with uncoated samples. The TAA-5/AS200 bilayer-coated electrode, in particular, demonstrates exceptional capacity retention (∼90.4%) and a specific discharge capacity of 146 mAh g-1 after 100 cycles at 1C within the voltage range of 2.2 to 4.6 V. The coated electrodes also show reduced voltage decay, lower surface film resistance, and improved interfacial charge transfer resistances, contributing to enhanced stability. The ALD-deposited TiO2/Al2O3 bilayer coatings exhibit promising potential for advancing the electrochemical performance of lithium-rich layered oxide cathodes in lithium-ion batteries.

Enhancing the power capability of lithium-rich manganese-based layered oxide cathodes by LaF3 modification

Lithium-rich manganese-based layered oxides, such as Li1.2Mn0.54Co0.13Ni0.13O2 (LNCM), are promising cathodes that possess both ultrahigh-specific capacity and high working voltage, yet they have not been commercialized due to intrinsic challenges. These challenges include sluggish Li-ion diffusion kinetics and structural degradation from the layered structure to a spinel-like form, leading to poor power capability and severe capacity fading. To address these challenges, we have developed a modification technique that involves fusing LaF3-decorated with La/F-doping. Protecting the electrode/electrolyte interface, inert LaF3 particles decorate on the LNCM surface impede interfacial side reactions. La-doping near the surface enlarges the Li layer spacing and facilitates Li-ion diffusion. A stronger TM-F bond is formed when F diffuses into the bulk phase and replaces O, thereby decreasing the migration of TM. The resulting LaF3-modified LNCM exhibits a high capacity of 256.1 mAh g−1 at 0.1C and a high-power capability of 3555 W kg−1 at 10C, which is 2.5 times higher than the pristine sample. We also elucidate the relationship between the structures (i.e., oxidation state of elements, bond energy, mechanical properties, and conductivity) and electrochemical behaviors (i.e., impedance and Li-ion diffusion) to explain why the modification of LaF3 improves the power property of the LNCM.

Effects of electrolyte/cathode ratio on investigation of their thermal behaviors using differential scanning calorimetry

Battery materials with high-energy density and good safety performance have been regarded as the ultimate target for larger-scale applications of lithium-ion batteries in electric transportation and grid energy storage. Thermal safety of high energy density cathode materials has been a hot topic for battery safety research in recent years. Differential scanning calorimetry (DSC) is widely used to investigate thermal reaction characteristics of battery materials, but the results are always affected by multiple variables, e.g., sample pre-processing and testing conditions. The variety of DSC results reported in literature have been perplexing the research community. Herein, the cathode-electrolyte system is chosen to reveal the changes of reaction mechanisms with different electrolyte/cathode ratios, since this system has been widely adopted to characterize thermal stability of cathodes and electrolytes in previous studies. Lithium-rich manganese-based layered oxide cathode and ester-based electrolyte are selected as representative samples. Our results reveal that flooded, sufficient, insufficient, and lean electrolyte conditions may lead to distinct thermal behaviors from probably different reaction routines, which may hold different reference values for battery-level safety analysis. This study also suggests the importance of systematic investigations on test conditions in battery material thermal safety research.

Unraveling and regulating superstructure domain dispersion in lithium-rich layered oxide cathodes for high stability and reversibility

Lithium-rich layered oxides (LLOs) have attracted tremendous attention as promising next generation cathode materials thanks to their superb capacity through additional anionic oxygen redox and lower cost by less use of expensive transition metals.

Building oxygen-rich vacancy coating for fast Li-ion diffusion kinetics and stable cycling of lithium-rich layered oxide cathode at wide-temperature

As a cathode with a high energy density for Li-ion batteries, Li-rich layered oxide (LLO) cathodes suffer from short lifespans and poor rate performance, mainly due to their irreversible lattice oxygen evolution leading to severe structural degradation and oxygen release. Herein, we propose the use of Zn-doped SnO2 coated with LLO cathode to tackle these issues. Compared to the traditional method of coating oxides on the surface of lithium-rich cathodes, Zn doping of SnO2 coating can artificially create abundant oxygen vacancies for LLO cathode, which can provide a buffer boundary for active oxygen generated by lithium-rich cathode during circulation, effectively promoting the reversible reaction of oxygen redox couple and stabilizing lattice oxygen. The experimental results show that the surface of the LLO cathode's Zn-doped SnO2 is rich in oxygen vacancies could significantly boost the kinetics of lithium ion transfer, and effectively inhibit layer-to-spinel phase transition, and lattice oxygen release. By taking advantage of the Zn-doped SnO2 coating, the capacity stability of LLO cathode is raised from 58.1 % to 86.7 % at 1C after 500 cycles and also obtains outstanding rate performance and cycling durability at wide-temperature (−10 to 55 °C).

Slab gliding, a hidden factor that induces irreversibility and redox asymmetry of lithium-rich layered oxide cathodes

Lithium-rich layered oxides, despite their potential as high-energy-density cathode materials, are impeded by electrochemical performance deterioration upon anionic redox. Although this deterioration is believed to primarily result from structural disordering, our understanding of how it is triggered and/or occurs remains incomplete. Herein, we propose a theoretical picture that clarifies the irreversible transformation and redox asymmetry of lithium-rich layered oxides by introducing a series of global and local dynamic structural evolution processes involving slab gliding and transition-metal migration. We show that slab gliding plays a key role in trigger/initiating the structural disordering and consequent degradation of the anionic redox reaction. We further reveal that the ‘concerted disordering mechanism’ of slab gliding and transition-metal migration produces spontaneously irreversible/asymmetric lithiation and de-lithiation pathways, causing irreversible structural deterioration and the asymmetry of the anionic redox reaction. Our findings suggest slab gliding as a crucial, yet underexplored, method for achieving a reversible anionic redox reaction.

Study on Attenuation Mechanism of High Energy Density Lithium Rich Battery Materials

The development of lithium rich layered oxide cathode materials with high energy density is one of the keys to improve the range of new energy vehicles. However, there are two bottlenecks in the development of this material: the voltage attenuation caused by structural transformation and the drastic decomposition of electrolyte at high voltage. In this paper, spherical Li1.2Mn0.54Co0.13Ni0.13O2 cathode material (LLO) was prepared, and the cycle performance of LLO cathode in LiBOB electrolyte with different content was compared. In addition, the effect of LiBOB electrolyte additives on lithium rich layered oxide materials was investigated. The decomposition path of LiBOB and the composition of stable CEI film were inferred by using computational chemistry and a variety of surface / interface detection methods.

Durable lithium-ion insertion/extraction and migration behavior of LiF-encapsulated cobalt-free lithium-rich manganese-based layered oxide cathode

Lithium-rich manganese-based cathode has made a subject of intense scrutiny for scientists and application researchers due to their exceptional thermal stability, high specific capacity, high operating voltage, and cost-effectiveness. However, the inclusion of cobalt, as a crucial component in lithium-rich manganese-based cathode materials, has become a cause for concern due to its limited availability and non-renewable nature, which eventually limits the growth of the battery industry and increase costs. Considering the poor stability of cobalt-free cathode, this work proposes a coating strategy of LiF through a simple high-temperature melting method. Directly coating LiF on Li1.2Ni0.2Mn0.6O2 surface is found to be an effective way to protect the cathode material, decrease metal solubility, and inhibit irreversible phase transition processes, thus leading to an improved electrochemical performance. As a result, the battery employing LiF coated Li1.2Ni0.2Mn0.6O2 cathode can be stabilized over 280 cycles and maintain a capacity of 110 mAh g−1 at 1C. What’s more, the mechanisms of ion insertion/extraction behavior and ion migration process are also studied systematically. This study will open the avenue to develop a high-energy battery system with cobalt-free cathode.

Enhancing Ionic Transport and Structural Stability of Lithium-Rich Layered Oxide Cathodes via Local Structure Regulation.

Lithium-rich manganese-based layered oxides (LRM) have garnered considerable attention as cathode materials due to their superior performance. However, the inherent structural degradation and obstruction of ion transport during cycling lead to capacity and voltage decay, impeding their practical applications. Herein, an Sb-doped LRM material with local spinel phase is reported, which has good compatibility with the layered structure and provides 3D Li+ diffusion channels to accelerate Li+ transport. Additionally, the strong Sb-O bond enhances the stability of the layered structure. Differential electrochemical mass spectrometry indicates that highly electronegative Sb doping effectively suppresses the release of oxygen in the crystal structure and mitigates successive electrolyte decomposition, thereby reducing structural degradation of the material. As a result of this dual-functional design, the 0.5 Sb-doped material with local spinel phases exhibits favorable cycling stability, retaining 81.7% capacity after 300 cycles at 1C, and an average discharge voltage of 1.87mV per cycle, which is far superior to untreated material with retention values of 28.8% and 3.43mV, respectively. This study systematically introduces Sb doping and regulates local spinel phases to facilitate ion transport and alleviate structural degradation of LRM, thereby suppressing capacity and voltage fading, and improving the electrochemical performance of batteries.

Effects of Lithium Source and Content on the Properties of Li-Rich Layered Oxide Cathode Materials

Lithium-rich layered oxide (LLO) are considered high-capacity cathode materials for next-generation lithium-ion batteries. In this study, LLO cathode materials were synthesized via the hydroxide coprecipitation method followed by a two-step lithiation process using different lithium contents and lithium sources. The effects of lithium content and lithium source on structure and electrochemical performance were investigated. This study demonstrated the clear impact of Li/TM ratio on electrochemical performance. Lower Li/TM ratio reduced the irreversible capacity loss in the first cycle and provided better cycling stability among all samples. The best results exhibited an initial discharge capacity of 279.65 mAh g−1 and reached a discharge capacity of 231.9 mAh g−1 (82.9% capacity retention) after 30 cycles. The sample using Li2CO3 as lithium source exhibits better electrochemical performance than the sample using LiOH as lithium source. Therefore, it is important to choose the appropriate lithium source and optimal lithium content for improving structural properties and electrochemical performance of LLO.

Manipulating Charge‐Transfer Kinetics of Lithium‐Rich Layered Oxide Cathodes in Halide All‐Solid‐State Batteries (Adv. Mater. 5/2023)

All-Solid-State Batteries The application of a lithium-rich layered oxide (LLO) cathode in all-solid-state batteries (ASSBs) has been hampered by its low electronic conductivity and the high reactivity of its lattice oxygen. In article number 2207234, Ruizhi Yu, Jiantao Wang, Xifei Li, Chandra Veer Singh, Xueliang Sun, and co-workers successfully address this by introducing an appropriate amount of conductive additives to the solid-state electrodes and manipulating the surface chemistry, realizing long-cycle-life LLO-based ASSBs.

A propanesultone-based polymer electrolyte for high-energy solid-state lithium batteries with lithium-rich layered oxides

A propanesultone-based polymer electrolyte with high ion transference number of ∼0.78 and wide electrochemical stability window of ∼5.0 V has been designed for solid-state lithium batteries with lithium-rich layered oxide cathode materials.

Integrating a Ferroelectric Interface with a Well-Tuned Electronic Structure in Lithium-Rich Layered Oxide Cathodes for Enhanced Lithium Storage

Li-rich layered oxides (LLOs) are considered promising candidates for new high-energy-density cathode materials for next-generation power batteries. However, their large-scale applications are largely hindered by irreversible Li/O loss, structural degradation, and interfacial side reactions during cycling. Herein, we demonstrate an integration strategy that tunes the electronic structure by La/Al codoping and constructs a ferroelectric interface on the LLOs surface through Bi0.5Na0.5TiO3 (BNT) coating. Experimental characterization reveals that the synergistic effect of the ferroelectric interface and the well-tuned electronic structure can not only promote the diffusion of Li+ and hinder the migration of On- but also suppress the lattice volume changes and reduce interfacial side reactions at high voltages up to 4.9 V vs Li+/Li. As a result, the modified material shows enhanced initial capacities and retention rates of 224.4 mAh g-1 and 78.57% after 500 cycles at 2.0-4.65 V and 231.7 mAh g-1 and 85.76% after 200 cycles at 2.0-4.9 V at 1C, respectively.